Penicillin Resistance of Pseudomonas aeruginosa Clinical Isolates from Urinary Tract Infections

One hundred and thirteen clinical isolates of Pseudomonas aeruginosa from urinary tract infections were tested for their mechanisms of resistance to penicillins. Ninety-eight percent and 100.0% of the strains were resistant (MIC≧100 μg/ml) to ampicillin and penicillin G, respectively, while only 5.3% were resistant to piperacillin. Low permeability of the outer membrane, and penicillinase production were involved in their resistance mechanisms. Peptidoglycan synthesis in ether-treated cells of two representative strains was inhibited by ampicillin and piperacillin at the concentrations markedly lower than that for penicillin G